The present invention relates to Radio Frequency (RF) electronic switches and, more particularly, to a RF switch for use in time division duplex (TDD) wireless communication systems.
Wireless communication systems such as 900 MHz cordless telephones often use a TDD methodology which allows the transmitter path of the telephone to be isolated from the receiver during the receive mode of operation and, likewise, isolate the receiver from the transmit path during the transmit mode.
One method that has been used to provide isolation uses four gallium arsenide switches arranged between the antenna and the transmit and receive paths of the wireless communication system. The four switches are controlled by a logic signal to be selectively opened or closed whereby the transmit path is both shorted to an alternating current ground and open-circuited to the antenna during the receive mode of operation while the receive path is directly connected to the antenna and vice versus. In this manner the receiver signal is coupled to the receiver circuitry of the system during the receive mode. The transmitter signal is isolated from the receiver signal path thereby being inhibited from desensitizing the receiver; wherein desensitizing refers to a large magnitude unwanted signal presence that limits the minimum detectable signal strength of the desired received signal. A major drawback of this technique is the significant cost of the gallium arsenide switches.
Hence, a need arises for reducing the manufacturing costs in wireless telephone communication systems while providing adequate isolation between the receiver and transmitter thereof.